1. Field of the Invention
This invention relates to circuit board contact elements and compliant sections thereof which are for mounting in plated-through holes in printed circuit boards, generally in conjunction with a header or other electrical connectors.
2. Description of Related Art
Electrical contacts, terminals or pins are used in the electronics industry in conjunction with printed circuit (PC) boards and panel boards for making electrical connections between, and among, circuits. The contacts have one end for making electrical contact with a conductive path on the PC board. The contacts have another end for electrical connection elsewhere. Many of the contacts have a compliant, contact or press fit end or section for forcing into a plated hole through the board deforming the compliant section. This results in an interference fit which is relied upon to hold the contact in the board and to provide an electrical connection between the contact and the material plating the hole. Such connections are solderless. It is also common to use multi-contact electrical connectors for connection to a printed circuit board or the like where each of the contacts has a compliant section.
In the past, the centers of holes in a circuit board were spaced about 0.1 inches (or about 2.540 mm) apart. The standard hole size in a printed circuit board was about 0.040 inches (or about 1 mm) in diameter with a manufacturing tolerance of plus or minus about 0.002 inches (or about 0.051 mm). A standard contact used for this size hole has a compliant section with a maximum dimension transverse to the insertion direction of 0.046 inches (or 1.18 mm). The compliant section deforms when forced into the hole. In order to be used for holes throughout the tolerance range, the contact only needs to be capable of deforming from about 10% up to about 21% of its maximum transverse thickness, i.e., its distance from one of its corners to its far corner. U.S. Pat. Nos. 4,655,537, 4,206,964 and 4,728,164 disclose contacts for mounting in traditional size holes having a diameter of 0.040 inches (or 1 mm) or greater.
To increase the number of electrical connections per unit area on a circuit board, boards have recently been produced with holes spaced about 0.050 inches (or about 1.27 mm) apart from center to center. If the hole size remained the same for such a board, the space on the board for providing conductive paths and insulative portions would be insufficient for most applications. As such, smaller hole sizes are desired or planned having diameters of about 0.024 inches (or about 0.6 mm) plus or minus about 0.004 inches (or about 0.1 mm) to provide more space for the conductive paths and insulative portions. Of course, whatever hole diameter is specified, manufacturers will still only be able to produce such holes with a tolerance of plus or minus about 0.002 inches (or about 0.051 mm). Furthermore, boards are being proposed much thinner than before. As a result, new smaller contacts are needed for connection to the smaller holes and thinner PC boards.
However, making the contacts smaller makes them more flexible and more likely to bend or distort. Furthermore, manufacturers of the boards still require a tolerance of plus or minus about 0.002 inches (or 0.051 mm) in making the holes. As a result, the contacts must now be capable of deforming at least 30% of its maximum transverse thickness. In other words, contacts must now be capable of press fitting and, thus, being retained by an interference fit in holes varying more in diameter in comparison to the size of the contact than previously existing contacts.
In view of these facts, it is desirable to provide a contact element and a compliant section thereof for insertion and conforming to holes having a large tolerance in relation to the hole size and, in particular, to small holes having a large tolerance.